B→K Transition Form Factor with Tensor Current within the kT Factorization Approach

We apply the kT factorization approach to deal with the B→K transition form factor with tensor current in the large recoil regions. Main uncertainties for the estimation are discussed and we obtain FT^B→K （0） = 0.25±0.01±0.02, where the first error is caused by the uncertainties from the pionic wavefunctions and the second is from that of the B-meson wavefunctions. This result is consistent with the light-cone sum rule results obtained in the literature.     

A Comparative Study of fB within QCD Sum Rules with Two Typical Correlators up to Next-to-Leading Order

The B-meson decay constant f_B is an important component for studying the B-meson decays, which can be studied through QCD sum rules. We make a detailed discussion on f_B from two sum rules up to next-to-leading order, i.e. sum rules I and II, which are derived from the conventional correlator and the correlator with chiral currents respectively. It is found that these two sum rules are consistent with each other. The sum rules II involves less non-perturbative condensates as that of sum rules I, and in principle, it can be more accurate if we know the dimension-four gluon condensate well. It is found that f_B decreases with the increment of m_B, and to compare with the Belle experimental data on f_B, both sum rules I and II prefer smaller pole b-quarkmass, m_b=4.68±0.07 GeV. By varying all the input parameters within their reasonable regions and by adding all the uncertainties in quadrature, we obtain f_B=172^{+23}_{-25} MeV for sum rules I and f_B=214_{-34}^{+26} MeV for sum rules II.     

Hadronic Decays of the Spin-Singlet Heavy Quarkomium under the Principle of Maximum Conformality

The principle of maximum conformality （PMC） provides a way to eliminate the conventional renormalization scale ambiguity in a systematic way. By applying the PMC scale setting, all non-conformal terms in a perturbative series are summed into the running coupling, and one obtains a unique, scale-fixed prediction at any finite order. In this study, we make a detailed PMC analysis for the spin-singlet heavy quarkoniums decay （into light hadrons） at the next-to-leading order. After applying the PMC scale setting, the decay widths for all those cases are ahnost independent of the initial renormalization scales. The PMC scales for ηc and he decays are below 1 GeV; to achieve a confidential pQCD estimation, we adopt several low-energy running coupling models to carry out the estimation. By taking the MPT model, we obtain Г（ηc → LH） = 25.09 -4.28^＋5.52 MeV, F（ηb →LH） 14.34-0.84^＋0.92 feV, Г（hc →LH） = 0.54-0.04^＋0.06 MeV and Г（hb →LH） = 39.89-0.46^＋0.28 keV, where the errors are calculated by taking mc E[1.4OGeV, 1.60GeV] and mb C[4.50GeV, 4.70GeV]. These decay widths agree with the principle of minimum sensitivity estimations, in which the decay widths of ηc,b are also consistent with the measured ones.     

Information on the pion distribution amplitude from the pion-photon transition form factor with the Belle and BABAR data

We perform an analysis of all existing experimental data on the pion-photon transition form factor (TFF). In the calculation, we include the next-to-leading order correction to the valence-quark contribution and estimate the non-valence-quark contribution by a phenomenological model based on the TFF's limiting behavior at both Q²→0 and Q²→∞. At present, the pion distribution amplitude (DA) is not de nitely determined, it is helpful to have a pion DA model that can mimic all the behaviors suggested in the literature. For the purpose, we adopt the conventional model for pion wavefunction/DA whose broadness is dominantly controlled by a single parameter B. We fix the DA parameters by using the CELLO, CLEO, BABAR and Belle data within small Q² region (Q²≤15 GeV²), where all the data are consistent with each other. The pion-photon TFF is then extrapolated into a larger Q² region. It is found that we still need more data at a large Q² region in order to determine the precise value of B, and we hope that the de nite behavior of pion DA can be concluded nally by the consistent data in the coming future.     

B-Meson Wavefunction by a Comparative Analysis of the B → π, K Transition Form Factors

Properties of the B-meson light-cone wavefunction up to next-to-leading order Fock state expansion are studied by a comparative study of the B → π, K form factors within the kT factorization approach and the light-cone sum rule analysis. The form factors F＋,0,T^B→ π and F＋,0,T^B→ K are carefully re-calculated up to O（1/mb^2） within the kT factorization approach in the large recoil region. The QCD light-cone sum rule is applicable in the large and intermediate energy regions, and the QCD light-cone sum rule results in Ref. [12] are adopted for such a comparative study. It is found that when the two phenomenological parameters ∧^-∈ [0.50, 0.55] and δ∈ [0.25, 0.30], the results of F＋,0,T^B→ π （Q^2 ） and F＋,0,T^B→ K（Q ^2） from these two approaches are consistent with each other in the large recoil energy region.     

Properties of the decay H→γγ using the approximate α_s~4 corrections and the principle of maximum conformality

The decay channel H→γγ is an important channel for probing the properties of the Higgs boson.In this paper,we analyze its decay width by using the perturbative QCD corrections up to the α_s~4 order with the help of the principle of maximum conformality(PMC).PMC has been suggested in literature for eliminating the conventional renormalization scheme-and-scale ambiguities.After applying PMC,we observe that an accurate renormalization scale independent decay width Γ(H→γγ) up to the N~4 LO level can be achieved.Taking the Higgs mass,M_H = 125.09±0.21 ±0.11 GeV,given by the ATLAS and CMS collaborations,we obtain Γ(H→γγ)|LHC = 9.364_(0.075)~(0.076) KeV.     

Novel and Self-Consistency Analysis of the QCD Running Coupling αs（Q） in Both the Perturbative and Nonperturbative Domains

The quantum chromodynamics（QCD） coupling αs is the most important parameter for achieving precise QCD predictions. By using the well measured effective coupling α_s^g1)（Q） defined from the Bjorken sum rules as a basis, we suggest a novel self-consistency way to fix the αs at all scales: The QCD light-front holographic model is adopted for its infrared behavior, and the fixed-order p QCD prediction under the principle of maximum conformality（PMC） is used for its high-energy be...     

Properties of the free energy density using the principle of maximum conformality

We present a detailed study on the properties of the free energy density at high temperature by applying the principle of maximum conformality(PMC)scale-setting method within effective field theory.The PMC utilizes the renormalization group equation recursively to identify the occurrence and pattern of the non-conformal{β_i}-terms,and determines the optimal renormalization scale at each order.Our analysis shows that a more accurate free energy density up to g_s~5-order level without renormalization scale dependence can be achieved by applying the PMC.We also observe that by using a smaller factorization scale around the effective parameter m _E,the PMC prediction is consistent with the lattice QCD prediction derived at low temperature.     

Revisiting the Twist-3 Distribution Amplitudes of K Meson Within the QCD Background Field Approach

In the present paper, we investigate the kaon twist-3 distribution amplitudes (DAs) φ p,σ K within the QCD background field approach. The SU f (3)-breaking effects are studied in detail under a systematical way, especially the sum rules for the moments of φ K p,σ are obtained by keeping all the mass terms in the s-quark propagator consistently. After adding all the uncertainties in quadrature, the first two Gegenbauler moments of φp,σ K are a K,p 1 (1 GeV)=0.376-0.148+0.103, a K,p 2(1 GeV) =0.701-10.491+0.48 , a K,σ1 (1 GeV) = 0.160-0.074+0.051, and a K,σ 2(1 GeV)=0.369-0.149+0.163 , respectively. Their normaliza- tion parameters μ K p |1 GeV=1.188-0.043+0.039 GeV and μ K σ |1 GeV=1.021-0.055+0.036 GeV. A detailed discussion on the properties of φ p,σ K moments shows that the higher-order s-quark mass terms can indeed provide sizable contributions. Furthermore, based on the newly obtained moments, a model for the kaon twist-3 wavefunction Ψ p,σ K (x, k ⊥ ) with a better end-point behavior is constructed, which shall be useful for perturbative QCD calculations. As a byproduct, we make a discussion on the properties of the pion twist-3 DAs.